Ionotropic GABAA receptors are ligand-gated ion channels that facilitate the passing of chloride ions across the cell membrane and promote an inhibitory influence on target neurons. These receptors are the major targets for benzodiazepines and related anxiolytic drugs. Bicuculline is a competitive GABAA receptor antagonist that can act as an allosteric inhibitor at GABAA receptors. At 100 μM, it blocks spontaneously opening chloride channels in the outside-out patches from the cultured cortical neurons. Bicuculline also reversibly blocks GABAA receptors on horizontal cells in the mouse retina with an IC50 value of 1.7 μM. By blocking the inhibitory action of GABA, bicuculline mimics the action of epilepsy and is widely used in experimental studies as a convulsant, inducing seizure in hippocampal or cortical neurons in prepared brain slices.
